Evolution of DS-1-like human G2P[4] rotaviruses assessed by complete genome analyses.

Group A rotaviruses (RVAs) are a leading cause of viral gastroenteritis in children, with G2P[4] RVA being one of the most common human strains worldwide. The complete genome sequences of nine G2P[4] RVA strains, selected from a 26-year archival collection (1985-2011) established in Palermo, Italy, were determined. A strain associated with a peak of G2P[4] RVA activity in 1996 resembled a reassortant strain identified in Kenya in 1982 and differed completely in genomic make up from more recent strains that circulated during 2004-2011. Conversely, the 2004-2011 G2P[4] RVAs were genetically more similar to contemporary RVA strains circulating globally. Recent G2P[4] strains possessed either single or multiple genome segments (VP1, VP3 and/or NSP4) likely derived from ruminant viruses through intra-genotype reassortment. Amino acid substitutions were selected and maintained over time in the VP7 and VP8* antigenic proteins, allowing the circulation of two contemporary G2P[4] variants to be distinguished. Altogether, these findings suggest that major changes in the genomic composition of recent G2P[4] RVAs occurred in the early 2000s, leading to the appearance of a novel variant of the DS-1-like genotype constellation. Whether the modifications observed in the neutralizing antigens and in the genome composition of modern G2P[4] RVAs may affect the long-term effectiveness of the vaccination programmes remains to be explored.